Common-rail injection systems are already known. In this case, said systems are injection systems for internal combustion engines, in which a high-pressure pump brings the fuel to a high pressure level. The pressurized fuel fills a pipe system which is continuously under pressure during operation of the engine.
Such a common-rail injection system is disclosed in DE 10 2006 023 470 A1. The system disclosed therein has a high-pressure fuel pump for delivering fuel, a high-pressure fuel accumulator connected to the high-pressure fuel pump for storing fuel at an injection pressure relative to the environment of the common-rail injection system, at least one injector connected to the high-pressure fuel accumulator for delivering fuel into at least one combustion chamber, a return line for returning fuel from the injector to the high-pressure fuel pump at a return line pressure relative to the environment of the common-rail injection system and an adjusting means for adjusting the return line pressure.
A further common-rail injection system is disclosed in DE 10 2006 026 928 A1. The system disclosed therein contains a fuel tank, a high-pressure fuel pump, a rail line, a pressure accumulator, an injector and a digital controller. In the supply line between the fuel tank and the high-pressure fuel pump, a volume flow control valve is arranged which is controlled by the digital controller via a volume control valve control line. The high-pressure fuel pump has at least one displacement unit. During operation of the injection system, it provides an injection pressure applied to the injector in the rail line.
Phase-gating controlled pumps provided with electrically actuated inlet valves also belong to the prior art, in which the inlet valve is opened in the currentless state.
Moreover, phase-gating controlled pumps provided with electrically actuated inlet valves are already known in which the inlet valve is closed in the currentless state. In this case, the inlet valve is kept closed by a spring. Without electrical control, such pumps are self-controlling due to the spring layout and the pressure ratios upstream and downstream of the inlet valve. Such a pump is not well suited to be a high-pressure pump as, in the case of a control malfunction which, for example, may be caused by a plug connector becoming detached, the aforementioned self control undesirably leads to full delivery of the pump. In such pumps, it is already known to use an overpressure valve in order to prevent the hydraulic system from rupturing due to the aforementioned full delivery of the pump.
In phase-gating controlled pumps provided with electrically actuated inlet valves, in which the valve is closed in the absence of current and the spring force is greater than the force resulting from the pressure difference (pressure upstream and downstream of the valve) the pump may not pump without electrical control of the inlet valve. This has the result that after the start-up of the internal combustion engine, i.e. after a start signal is present, initially the phase position of the plunger of the pump has to be identified in order to be able to synchronize the electrical control of the inlet valve with the rotation of the crankshaft. This, in turn, has the result that the pressure build-up and thus also the engine start-up are delayed.